Waterproofing Basics: A Plain-Language Glossary

If you've landed on one of our product comparison articles and hit a term like “elongation” or “crack bridging” without knowing what it means, you're in the right place. This page explains the handful of concepts that come up again and again across waterproofing product datasheets — in plain language, without assuming you already know the field. Once these make sense, every comparison article and product page on this site will read a lot more clearly.

If you want the full picture across every waterproofing chemical family instead of just the vocabulary, see the Types of Waterproofing Chemicals guide.

The Words You'll See on Every Datasheet

ELONGATION

This is how far a coating can stretch, as a percentage of its original length, before it tears. A concrete slab expands and contracts with heat and cold, and hairline cracks open and close slightly over the seasons. A coating with higher elongation (some go past 400–700%) moves with that cycle without splitting. A coating with lower elongation (closer to 100–150%) relies more on being strongly bonded to the surface to stay intact under the same movement, rather than stretching to absorb it. Neither approach is “better” in isolation — it only matters relative to how much the surface underneath actually moves, and what role the coating is playing (a bonded base layer vs. an exposed flexible membrane).

CRACK BRIDGING

This is the widest existing crack a coating can span and still stay watertight, without the crack telegraphing through and reopening the coating above it — usually stated in millimetres (for example, “bridges cracks up to 2mm”). It's a different number from elongation: elongation is about the coating's own material stretching, crack bridging is about how wide a specific gap it can physically span without failing at that gap. Anything wider than a product's rated limit needs to be mechanically sealed first — typically by widening the crack into a V-groove and filling it with a dedicated crack sealant — before the waterproof coating goes on top. A coating is not a substitute for crack repair; it's applied after crack repair.

TENSILE STRENGTH AND ADHESION STRENGTH

Two different numbers that both sound like “how strong is it.” Tensile strength is how much pulling force the cured film itself can take before it tears — a property of the material. Adhesion (or bond) strength is how hard it is to pull the coating off the substrate — a property of the bond between the coating and the concrete underneath it. A coating can have excellent tensile strength and still fail if its adhesion is poor on a dirty or unprepared surface, which is part of why surface preparation matters as much as the product itself.

DURABILITY / SERVICE LIFE

The number of years a manufacturer rates a product for under correct application and normal conditions. This is a design rating, not a guarantee that ignores installation quality — a coating applied over a poorly prepared surface, without the stated primer, or at less than the specified thickness will generally not reach its rated service life, whatever the datasheet says.

COVERAGE (sq.ft or m² per litre/kg per coat)

This tells you how much material one coat uses across a given area — it's a purchasing number, used to work out how much product to buy for a given surface area and number of coats. It is not an application-count number: buying enough material for the stated coverage and actually applying the full specified number of coats at full thickness are two separate requirements, and skimping on either produces the same result — a thinner film than the product was tested at, and a shorter real-world life than the rated one.

A Few More Terms Worth Knowing

SINGLE COMPONENT VS. TWO COMPONENT

This tells you how the product arrives and how much site work is needed before it goes on. A single component (1K) product comes ready to use straight from the container — stir and apply. A two component (2K) product is supplied as two parts (commonly a liquid and a powder, or a base and a hardener) that have to be mixed together on site in a stated ratio before application, and once mixed, has a limited working time (see Pot Life, below). Two-component systems are common where the reaction between the two parts is what gives the coating its final strength or chemical resistance — the trade-off is that mixing ratio and mixing time now matter as much as the product itself.

POSITIVE SIDE VS. NEGATIVE SIDE WATERPROOFING

This describes which side of the structure the coating is applied to, relative to where the water is coming from. Positive side waterproofing is applied on the same side the water pushes from — for example, coating the outer face of a basement wall before backfilling it, so water never reaches the concrete at all. Negative side waterproofing is applied on the opposite, dry-facing side — typically because the wet side is inaccessible, such as the inside face of an existing basement wall you can't dig up. Positive side is generally preferred where it's possible to build it in, because it stops water reaching the structure in the first place; negative side is a repair-and-retrofit approach, and needs a product specifically rated to work against hydrostatic pressure (see below) pushing from the wrong direction.

HYDROSTATIC PRESSURE

This is the pressure exerted by standing or accumulated groundwater pushing against a structure — a basement wall below the water table, or a water tank wall from the inside. It's stated on some datasheets as a pressure rating (for example, in metres of water head) that a product can resist without being forced off the substrate. A coating that isn't rated for hydrostatic pressure can work perfectly well against surface dampness or light rain and still fail against sustained groundwater push, which is why “waterproof” alone isn't enough information — waterproof against what, and from which side is the real question for below-ground work.

POT LIFE

For any product mixed on site (see Single vs. Two Component, above), pot life is the window of time after mixing during which the material stays workable and can still be applied properly. Once pot life expires, the material starts to set in the container or on the tools rather than on the surface, and using it past that point produces a poorer bond and finish even if it still looks liquid. Pot life is a site-logistics number as much as a technical one — it decides how much area a crew can realistically cover per batch.

VOC CONTENT

Volatile Organic Compound content is a measure of the solvents that evaporate out of a coating as it cures, expressed in grams per litre. It matters for two practical reasons: worker safety and ventilation requirements during application (a high-VOC product needs better ventilation, especially in enclosed spaces like water tanks or basements), and, increasingly, green-building compliance where projects specify a maximum VOC limit for interior-facing products.

SOLIDS CONTENT

This is the percentage of a liquid coating that remains behind as a dry film once the water or solvent carrier evaporates during curing — the rest is what flashes off. A higher solids content generally means more actual film thickness per coat from the same litre of material, which is one reason two products with the same “coverage per litre” figure can still end up with different final dry film thickness.

SHORE HARDNESS

A rating of how hard or soft a fully cured coating is, most often relevant for products that stay exposed on a walkable or trafficked surface (a terrace, a podium deck) rather than being covered by tiles or backfill. It's a trade-off indicator, not a “bigger is better” number: a harder film generally resists foot traffic and abrasion better, while a softer, more flexible film generally has more give to move with the substrate. Which one is right depends on whether the surface will be walked on directly or protected by a covering.

SERVICE TEMPERATURE RANGE

The range of temperatures a cured coating is rated to perform in without degrading, cracking, or losing adhesion — relevant on exposed roofs and terraces that see direct sun. This is different from application temperature (the surface and air temperature the product must be applied within, stated separately on most datasheets); a coating can have a wide service range once cured while still requiring a much narrower temperature window during application itself.

SRI (SOLAR REFLECTANCE INDEX) / HEAT REFLECTIVITY

A rating of how much solar heat a coating's surface reflects rather than absorbs, most relevant to reflective/“cool roof” terrace coatings. A higher SRI generally means a cooler roof surface and, in turn, a cooler room below it — this is a comfort and energy-use figure layered on top of a product's core waterproofing performance, not a substitute for it; a coating still needs to meet its elongation, crack bridging, and durability ratings regardless of how reflective it is.

Structural Repair Terms You'll See Alongside Waterproofing

Waterproofing is often specified together with structural repair, because a waterproofing coating is not a substitute for fixing damage to the concrete underneath it — it's applied after that damage is repaired. These terms come up in that repair scope:

SPALLING

Concrete that has cracked and broken away in chunks or flakes, exposing the layer underneath — most often caused by the reinforcement bar inside corroding, expanding, and pushing the surrounding concrete apart from the inside. Spalled concrete has to be cut back to sound material and repaired before any coating goes over it; coating over spalled concrete just seals in a structural problem that will keep spreading underneath.

HONEYCOMBING

A porous, gap-riddled patch of concrete that looks like its namesake, caused by the concrete not compacting or flowing properly around reinforcement during the original pour. It's a weak point that lets water in easily and needs to be cut out and made good with a repair mortar before waterproofing, rather than simply coated over.

HAIRLINE CRACKS VS. STRUCTURAL CRACKS

A hairline crack is fine, shallow, and generally a surface/shrinkage crack that most waterproofing coatings can bridge directly (see Crack Bridging, above) once it's within the product's rated width. A structural crack is wider, often follows a straight or stepped line, and indicates movement or a load-related issue in the structure itself — this needs an engineer's assessment and structural repair, not just a wider crack-bridging coating, because the coating doesn't address why the crack is there or forming in the first place.

EXPOSED REBAR & CORROSION

When spalling or long-term water ingress exposes the steel reinforcement bar inside concrete, that steel starts to rust once it's in contact with air and moisture — and rusted steel takes up more volume than clean steel, which is what causes the spalling in the first place, making this a self-feeding cycle if left untreated. Repair typically involves cleaning the exposed bar back to bright metal, applying a rust-converter or anti-corrosive primer rated for the purpose, and then rebuilding the concrete section before any waterproofing coat is applied over the repaired area.

Standards and Certifications You'll See Referenced

Concrete & Admixture Terms You'll See in Technical Datasheets

These come up mostly on admixture and plasticizer datasheets — products mixed into concrete or mortar itself, rather than coated on top of it.

PLASTICIZER / SUPER PLASTICIZER (WATER REDUCER)

An admixture mixed into concrete that lets you use less water for the same workability, or get better workability for the same water — the two are the same trade-off stated from opposite ends. Less water in the mix (for the same cement content) generally means denser, stronger, less permeable concrete once it cures. “Super” plasticizers simply do this more efficiently than standard ones, letting the water reduction go further without making the mix impossible to place.

WORKABILITY

How easy freshly-mixed concrete or mortar is to place, compact, and finish — pour it, vibrate it into a mould, trowel it smooth — before it starts to set. A mix can be strong on paper and still be a problem on site if it's too stiff to work with in the time available, which is why plasticizers exist: to improve workability without just adding more water (which would weaken the cured concrete).

PERMEABILITY & CAPILLARY ABSORPTION

Permeability is how easily water can pass through a material; capillary absorption is water being drawn up or into a material through its own fine pores, the way a paper towel wicks up a spill, independent of any outside pressure pushing it. Reducing both is the whole point of an integral waterproofing admixture — it makes the concrete itself resist water entry, rather than relying only on a coating applied afterward.

HYDROPHOBIC

Literally “water-fearing” — a material or additive that actively repels water rather than merely resisting it passing through. An admixture described as giving a “hydrophobic advantage” is doing more than reducing permeability; it's making the concrete's internal pore surfaces repel water on contact.

RETARDER

The opposite of a set accelerator (below) — an admixture that slows down how fast concrete sets and hardens. Used where a longer working window is needed: large pours, hot weather (which speeds up setting on its own), or when concrete has to be transported a long distance before placing.

SET ACCELERATOR

An admixture that speeds up how fast concrete sets and gains early strength — useful for emergency repairs, cold-weather concreting (which naturally slows setting), or sprayed concrete (shotcrete/gunite) that needs to grip a surface quickly, including overhead or vertical applications, without sagging or falling off.

SELF-COMPACTING CONCRETE

A highly flowable concrete mix, achieved with plasticizers, that fills formwork and flows around dense reinforcement under its own weight — without needing mechanical vibration to compact it. Useful where reinforcement is too congested for a vibrator to reach properly, or where vibration noise/access is a constraint.

CHLORIDE-FREE

A claim that an admixture contains no chloride salts. This matters specifically for reinforced concrete, because chlorides accelerate the corrosion of the steel reinforcement bar inside it (see Exposed Rebar & Corrosion, above) — an admixture that isn't chloride-free can undermine the very structure it's meant to protect, even while improving the concrete's other properties.

CARBONATION

A slow chemical reaction where carbon dioxide from the air reacts with concrete over years, gradually lowering its natural alkalinity. Concrete's high alkalinity is what normally keeps the steel reinforcement inside it from rusting; once carbonation reaches the depth of the rebar, that protection is lost and corrosion can begin. This is why some coatings and admixtures are specifically described as “anti-carbonation” — they slow CO₂ from penetrating the concrete in the first place.

EFFLORESCENCE

The white, chalky, powdery deposit that sometimes appears on masonry, plaster, or concrete surfaces. It forms when water moving through the material dissolves salts inside it, carries them to the surface, and leaves them behind as the water evaporates. It's a visible symptom of water movement through the material — treating it cosmetically without addressing why water is getting in and moving through in the first place usually means it comes back.

More Repair, Grouting & Coating System Terms

ELASTOMERIC

Describes a material that behaves like rubber — it stretches significantly under load and springs back to close to its original shape once the load is removed, rather than staying deformed or cracking. Most flexible waterproofing coatings are described as “elastomeric” specifically because this stretch-and-recover behaviour is what lets them move with a substrate's seasonal expansion and contraction (see Elongation, above) instead of splitting.

MEMBRANE (JOINTLESS / SEAMLESS)

In waterproofing, a “membrane” just means the continuous waterproof layer formed once a liquid coating cures — not a pre-made sheet material. “Jointless” or “seamless” describes an advantage of liquid-applied systems specifically: because the coating is poured or brushed on as a liquid and cures in place, there are no overlapping sheet joints for water to eventually find and exploit, unlike a pre-formed membrane sheet that has to be seamed together on site.

SUBSTRATE

The surface a coating, adhesive, or grout is being applied onto — the concrete, masonry, plaster, or metal underneath. Most application instructions and warranty conditions are stated relative to substrate condition (clean, sound, properly prepared) because a product's rated performance figures are tested under those conditions, not on a dirty or unsound surface.

BOND COAT / BONDING AGENT

A liquid or slurry applied first to help a new layer of concrete, mortar, or plaster stick properly to an existing, already-hardened surface — two surfaces of different ages otherwise don't bond well on their own. Common at repair boundaries: where new patch material meets old, sound concrete.

SCREED

A layer of mortar or concrete laid on top of a structural slab to bring a floor to its finished level and falls (slope), before the final flooring or waterproofing goes on. On a terrace, this is usually the layer that's sloped to direct water toward a drain.

NON-SHRINK GROUT

A grout formulated so it doesn't shrink as it cures and dries — ordinary cement mixes shrink slightly, which would leave a gap under a base plate or in a structural gap-fill where full, continuous contact matters (for example, under machinery bases or bridge bearings). Some non-shrink grouts are also mildly expansive, to actively compensate for any shrinkage rather than merely avoiding it.

INJECTION GROUT / INJECTION RESIN

A liquid grout (polyurethane, epoxy, or acrylic-based) pumped under pressure through a drilled hole or port into a crack, void, or leak path inside concrete or masonry — rather than applied to a surface. Used to seal active water leaks or fill internal voids that a surface coating can't reach. Some are “water-reactive,” meaning they expand and cure on contact with water specifically, which is what lets them seal an active, flowing leak rather than just a dry crack.

ANCHOR GROUT

A specific type of grout used to fix bolts, dowels, or reinforcement bars firmly into a drilled hole in concrete or rock — for example, fixing a foundation bolt or a machinery base plate. It's chosen for high early strength and strong bond rather than for waterproofing, though some anchor grouts are also water- and chemical-resistant.

PLUGGING COMPOUND

A fast-setting compound — sometimes setting in under a minute — used to physically stop an actively flowing water leak on the spot, often by hand, before a proper waterproofing repair is carried out. It's an emergency stop-gap step, not a substitute for the actual repair that follows it.

CRYSTALLINE WATERPROOFING / CRYSTALLIZATION

A cement-based waterproofing system that works chemically rather than by just forming a surface film. Certain chemicals in the product react with moisture and un-hydrated cement inside the concrete to grow needle-like crystals that fill the concrete's own internal capillaries and micro-cracks from within. Because this crystal growth happens throughout the depth of the concrete (not just at the surface), a crystalline treatment can still self-seal a minor future hairline crack if moisture reaches it later, and it's a common choice for negative-side waterproofing (see above) since it works from either face of the concrete.

OSMOTIC PRESSURE / OSMOTIC PROPERTIES

A natural physical process where water is drawn through a semi-permeable material (like concrete) from a lower-salt-concentration side toward a higher-concentration side, even against gravity or an applied coating. It's specifically relevant to negative-side and underground waterproofing, where groundwater can be drawn through a wall this way over time — a coating rated for “osmotic resistance” is claiming it can withstand this pull without blistering or debonding.

MICRO CONCRETE

A specially graded, flowable concrete repair mix used to reinstate sections of damaged or removed concrete, particularly where reinforcement is congested or the repair section is narrow — its fine, controlled aggregate grading lets it flow and fully surround reinforcement in situations ordinary concrete couldn't reach or compact into.

CURING COMPOUND

A liquid sprayed or brushed onto freshly-poured, still-green concrete to form a temporary film that slows water evaporation from the surface. Concrete needs sustained moisture in its first days to gain strength properly (this is “curing”); losing that moisture too fast to evaporation causes weak surfaces and shrinkage cracking. A curing compound is a practical substitute for continuously wetting a slab by hand or ponding water on it.

RUST CONVERTER / ZINC-RICH PRIMER

Two related but different approaches to protecting already-rusted steel reinforcement or structural steel before it's coated or covered again. A rust converter chemically reacts with existing rust to convert it into a more stable, paintable compound, rather than requiring the rust to be fully removed first. A zinc-rich primer instead relies on zinc particles in the primer sacrificially corroding in place of the steel underneath (the same principle as galvanizing), giving ongoing protection even if the coating is later scratched.

SELF-LEVELING (FLOOR COATINGS)

A flooring product formulated to flow out and find its own flat, level surface once poured, needing minimal manual spreading — used for epoxy floor toppings and screeds where a smooth, seamless, level finish over a larger area is the goal.

FLOOR HARDENER (DRY SHAKE)

A hard-wearing material (metallic or non-metallic aggregate blended with cement) shaken dry onto a freshly-poured concrete floor slab while it's still wet, then trowelled in, so it bonds into the top surface of the slab itself rather than sitting on top as a separate coating. Used on industrial floors that need much higher abrasion resistance than plain concrete offers, without adding a full separate topping system.

WATER REPELLENT (SILICONE-BASED)

A clear, breathable, penetrating treatment (distinct from a film-forming coating) that causes water to bead and run off a masonry or concrete surface rather than soaking in, while still allowing trapped internal moisture and water vapour to escape outward. Because it doesn't form a visible film, it's typically chosen where the original look and texture of a surface (exposed brick, natural stone, textured concrete) needs to be preserved.

ALIPHATIC VS. AROMATIC (POLYURETHANE)

A distinction in the chemistry of a polyurethane coating that determines how it behaves in sunlight over time, not its waterproofing performance directly. An aliphatic polyurethane resists UV rays well and holds its colour and gloss with minimal yellowing over years of sun exposure — the right choice for any coating left permanently exposed. An aromatic polyurethane yellows and chalks under prolonged UV exposure and is generally used only where it will be covered by something else afterward, or isn't exposed to direct sunlight long-term.

POLYUREA VS. POLYURETHANE

Both are elastomeric coating chemistries, often used for similar waterproofing jobs, but they cure differently. Polyurethane cures through a reaction with moisture (from the air or the substrate), which generally makes it more forgiving of an imperfectly dry surface but slower to fully cure. Polyurea cures through a much faster internal chemical reaction between its own two components, giving a touch-dry, walkable film in seconds to minutes rather than hours — useful where a surface needs to be back in service almost immediately — but it demands more precise, professional spray-application equipment to apply correctly. A “hybrid polyurea-polyurethane” system, as the name suggests, blends both to balance fast cure speed with easier application.

GUN GRADE VS. POUR GRADE (SEALANTS)

Describes a sealant's consistency and how it's applied, not its chemistry. Gun grade is a paste-like consistency, dispensed from a caulking gun into vertical or overhead joints where it needs to stay in place without sagging. Pour grade is a self-levelling, more liquid consistency, poured directly into horizontal joints (like a floor expansion joint) where it's able to settle flat on its own.

LOW MODULUS SEALANT

“Modulus” describes how much force a sealant resists as it's stretched. A low-modulus sealant stretches easily under relatively little force, making it well suited to joints that move a lot (thermal expansion joints, for instance) since it won't tear itself away from the joint faces or pull the substrate as it flexes.

PRIMERLESS ADHESION

A claim that a sealant or coating bonds directly and reliably to a stated range of surfaces without needing a separate primer coat first — simplifying and speeding up application, provided the surface is still clean and properly prepared (primerless doesn't mean prep-free).

Waterproofing vs. Damp-Proofing: Not the Same Thing

Application Questions People Usually Ask Only Once They're On Site

DO I NEED A PRIMER?

It depends on the surface, not the coating. A clean, sound, absorbent concrete surface generally doesn't need one. A dense, painted, or previously-coated surface, or one with old bitumen residue, usually needs a primer (or a coat specifically rated to bond to that substrate) so the new coating keys in properly instead of sitting loose on top of contamination. Skipping primer where it's needed is one of the most common causes of a coating peeling within the first year — not a coating “failing,” but a bonding step that was never done.

HOW MANY COATS DO I ACTUALLY NEED?

Most liquid-applied waterproofing coatings are specified for a minimum of 2 coats — not because one coat “half-works,” but because a single coat is thin and uneven enough to have pinholes; the second coat, applied in the opposite direction to the first, closes those gaps and brings the total film up to its rated thickness. On a weak, aged, or previously-damaged slab, that can extend further, to a multi-layer reinforced system: a base coat, a mesh or fabric reinforcement embedded into it while still wet, then additional coats over that. More layers aren't overkill — they're what the surface condition actually calls for.

HOW LONG BEFORE I CAN WALK ON IT, OR LET WATER SIT ON IT?

Curing time and foot-traffic time are different things, and mixing them up is a common site mistake. A coating can be dry to the touch well before it's fully cured — walking on it, filling a tank, or letting water pool on it too early can dent, mark, or disturb a film that hasn't finished curing. Always follow the specific product's stated cure time rather than judging by touch.

CAN I APPLY A NEW WATERPROOFING COATING OVER AN OLD ONE?

Sometimes, but it depends on the condition of what's already there, not just what's convenient. A sound, well-bonded existing coating can often be recoated directly. A failing, flaking, or blistered one needs to be removed — or at minimum have the loose material scraped back to sound substrate — first. Coating over a failing layer just seals the failure in underneath the new one, where it will eventually telegraph back through.

WHY DO SOME PRODUCTS NEED CEMENT MIXED ON SITE, AND OTHERS DON'T?

It comes down to what the finished coating is designed to do. A cementitious (cement-based) coating is built to become part of a rigid, bonded system — the cement in the mix is what lets it key structurally into concrete and accept tile adhesive on top, so it needs cement to do its job. A pure acrylic or polymer coating is built to stay a flexible, moving surface film, where adding cement would make it more rigid — working against the elongation it's designed around. Neither approach is more “advanced” than the other; they're built for opposite roles, and the right one depends on whether the surface is going to be covered (tiled, screeded) or left exposed.

The One Question Worth Asking Before Any of the Above

None of these terms tell you which product to use on their own — they tell you how to read a datasheet once you already know what you're dealing with. Before comparing numbers, it helps to know: is the surface going to be covered (tiled, plastered, backfilled) or left exposed? Is the water condition standing/pressure-driven or just occasional rain and dampness? And how much does the surface actually move seasonally? Those three answers, more than any single spec figure, point toward the right family of product — covered in full in the Types of Waterproofing Chemicals guide.